Filter felts which comprise a supporting screen and a batt of staple fibers hydraulically entangled into the scrim are described in Frankenburg U.S. Pat. 4,612,237. In this patent, the staple fibers may be a blend of poly(tetrafluoroethylene) fibers and glass fibers, and the scrim may comprise glass fibers or woven poly(tetrafluoroethylene) yarns or stainless steel, polyamide, or polyphenylene sulfide.
U.S. Pat. No. 4,361,619 to Forsten et al. describes a filter felt made by needling a blend of staple fibers of glass and poly(tetrafluoroethylene) fibers to a scrim of poly(tetrafluoroethylene) fibers.